Nitrogen, potassium, and phosphorus are essential elements for plant growth, and commercially available fertilizers invariably contain one or more of these elements. Unfortunately most of the commercial fertilizers containing these elements are readily water soluble and this creates a number of disadvantages. In a heavy rainfall much of the fertilizer may be dissolved in the rainwater and soaked into the ground below the plant roots or rapidly transported away by flowing surface water. This fertilizer never becomes available to the plants. Another disadvantage is that the fertilizer often becomes available to the plant too rapidly resulting in injury to the plant rather than benefit. This is often noticed in "burned" lawns or crops. Thus, it would be desirable to have a fertilizer formulation that enhances slow release of the fertilizer.
The following prior art is of interest:
The article "Polymer Coating on Urea Prills to Reduce Dissolution Rate" by Omar A. Salman, Journal of Agricultural Food and Chemicals, 36, pp. 616-621 (1988) describes the need for slow release urea formulations and the process for producing low density polyethylene coated urea.
L. Woerther, U.S. Pat. No. 3,096,171 (1960) describes the process for producing slow release fertilizer formulations by coating granules with plant waxes.
J. C. Mason, Jr., U.S. Pat. No. 3,205,061 (1964) describes the process for producing slow release urea by dispersing urea in paraffin wax.
R. C. Fox, U.S. Pat. No. 3,372,019 (1968) describes the process for producing slow release fertilizer formulations by coating granules with a mixture of paraffin or microcrystalline wax and resin comprised of copolymers of ethylene and vinyl acetate.
A. R. Shirley and R. S. Meline, U.S. Pat. No. 3,903,333 (1975) describe the process for producing slow release urea by coating granules with molten sulfur.
J. M. H. Lambie, U.S. Pat. No. 4,657,576 (1987) describes the process for producing slow release fertilizers by coating granules with dicyclopentadiene/linseed oil.
None of the prior art references teach the use of medium density polyethylene wax in a fertilizer formulation.